1. Field of the Invention
The present invention relates to a semiconductor chip and a method of producing the same.
2. Description of Related Art
Internal wiring in a semiconductor chip is generally composed of aluminum or the like in order to hold down the production cost. The wiring composed of aluminum or the like is subjected to oxidation by moisture. Therefore, a surface of the wiring is covered with a surface protective film composed of silicon nitride, for example. An opening is formed on the surface protective film to expose a part of the wiring, thereby forming a pad for external connection used for connection to an external terminal such as a lead terminal. An end of a wire composed of gold (Au) for example, is made to adhere and connected to the external connection pad, and the other end of the wire is connected to the external terminal, thereby achieving electrical connection between the wiring in the semiconductor chip and the external terminal.
After the wire is connected to the external connection pad, it is preferable that the surface of the pad is completely covered with the wire. When the adhesion area of the wire on the external connection pad is small, however, the surface of the pad is not completely covered with the wire, so that a part of the pad may remain exposed. Because the pad is composed of aluminum or the like, if the pad is exposed, it may be oxidized by moisture or the like and corroded.
An object of the present invention is to provide a semiconductor chip in which a pad for external connection may not be corroded irrespective of a connected state of a wire and a method of producing the same.
Another object of the present invention is to provide a semiconductor device having a chip-on-chip structure using the above-mentioned semiconductor chip and a method of producing the same.
A semiconductor chip according to the present invention comprises a surface protective film for covering internal wiring; an external connection pad which is formed by partially exposing the internal wiring from the surface protective film; and a wire connecting portion which is formed using a metal material having oxidation resistance on the external connection pad and to which a wire for electrical connection to an external terminal is connected.
According to the present invention, the wire connecting portion composed of a metal material having oxidation resistance is formed on the external connection pad. In other words, the surface of the external connection pad is covered with the wire connecting portion composed of the metal material having oxidation resistance. Consequently, the external connection pad is not exposed to the exterior irrespective of a connected state of the wire to the wire connecting portion. Accordingly, the external connection pad may not be oxidized by moisture or the like and corroded.
The semiconductor chip may be overlapped with and joined to a surface of another solid device (for example, another semiconductor chip) in a state where the surface protective film is opposed to a surface of the solid device. In this case, it is preferable that the semiconductor chip further comprises an internal connection (chip connecting pad) which is formed by partially exposing the internal wiring from the surface protective film in a portion different from the external connection pad, and a bump formed in a raised state on the internal connection pad (chip connecting pad) using a metal material having oxidation resistance in order to make electrical connection to the solid device.
Furthermore, in this case, it is preferable that the wire connecting portion is composed of the same material as that for the bump. Consequently, it is possible to form the wire connecting portion at the same step as the bump.
A method of producing a semiconductor device according to the present invention is a method of producing a semiconductor chip which is to be overlapped with and joined to a surface of another solid device (for example, another semiconductor chip), comprising the steps of stacking a surface protective film on internal wiring; forming an opening on the surface protective film to partially expose the internal wiring, to form an external connection pad and an internal connection pad (chip connecting pad); and selectively plating (preferably, plating with a material having oxidation resistance) the external connection pad and the internal connection pad (chip connecting pad), to respectively form a wire connecting portion to which a wire for electrical connection to an external terminal is connected and a bump for electrical connection to the other semiconductor chip.
According to the method, the wire connecting portion can be formed at the same step as the bump. Accordingly, the number of steps of producing the semiconductor chip is not increased by providing the wire connecting portion on the external connection pad.
It is preferable that the wire connecting portion is composed of the same material as that for the wire. Consequently, it is possible to improve the adhesive properties of the wire to the wire connecting portion.